This invention relates in general to machining processes, and in particular to a process for machining a flexible foam.
Flexible foams such as polyurethane foams are used in many different commercial applications. In a typical application the flexible foams are used for padding. For example, the flexible foams can be formed into the shape of foam pads for vehicle seats.
Flexible foams are usually molded into a desired shape. However, in some situations it would be advantageous to be able to machine a flexible foam to create a desired shape, for example, to produce prototype foam pads for vehicle seats. Unfortunately, a flexible foam such as a polyurethane foam is very difficult to machine due to its flexible nature. The cutting tools of conventional automated cutting equipment catch and tear the foam instead of cutting it. As a result, it is a common practice to cut the flexible foam by hand instead of using automated equipment such as a CNC milling machine, even when CADD data is available to produce cutter paths for the automated equipment. Cutting by hand is slower and not as accurate as cutting with automated equipment.
U.S. Pat. No. 6,273,697 B1 to Harfmann, issued Aug. 14, 2001, discloses a process for forming a low-density polymer foam article in which a blowing agent and a resin are combined to form a mixture, and the mixture is cooled to a temperature approaching its freezing point and then extruded. The extruded foam is then cooled by direct contact with a cooling surface. In the embodiment shown in FIG. 1, a knife is used to slit the foam to create a sheet, which is then wound into rolls. There is no suggestion in this patent to start with a flexible foam, and then to treat the flexible foam to temporarily harden it before cutting. The patent discloses a rigid foam used to make an article such as a food container, not a flexible foam adapted for use as padding or the like. Moreover, the disclosed process cools the foam to condense the blowing agent, not to harden the foam to make it easier to cut.